Directional hearing aid



July 29, 1969 O. HASSLER DIRECTIONAL HEARING AID Filed D90. 6, 1966MICROPHONE MICROPHONE -RECEIVER AM PLIFIER l kl) INVENTOR. 0rr0 HASSLEEBY I I g United States Patent US. Cl. 179-107 7 Claims ABSTRACT OF THEDISCLOSURE A directional hearing aid with two microphones mounted inback to back relationship. An acoustic resilient seal disposed aroundthe aperture between one of the microphones and a forward facing openingin the housing. A flexible conduit is disposed between the othermicrophone and a rearward facing opening in the hearing aid.

People hard of hearing often find fault with their hearing aid in thatit does not give them any indication as to the direction from which thesources of sounds emanate. People wearing such hearing aids, even of thespectacle type or hearing aids form behind the ear, are not in the habitof turning their head in the direction of the sound they hear, becausethey generally use their eyes to assist their hearing, and therebyobtain the known advantageous effect of simultaneously sensing an eventwith both organs.

It is general knowledge that the sound pick-up characteristics of themicrophone employed in the hearing aids is such that sound may be pickedup from all directions which causes the apparatus to receive the soundequally well no matter from which direction it may come.

Because of the general microphone characteristics a directional sounddetection is excluded and causes considerable difiiculties in noisyrooms or, if several people are participating in a discussion and allspeaking at the same time, The condition is made worse when a personhard of hearing in both ears wears a hearing aid for one ear only.

The present invention contemplates a combination of two hearing aidmicrophones suitably used as an electroacoustic transducer for a hearingaid, the microphones being arranged in such a manner that they lie in aback-toback relationship. Furthermore, in accordance with the invention,the directional effect may be obtained by arranging a microphone behinda forwardly directed sound opening and in front of a sound passageopening to the rear of the housing, whereby the sound is conveyed to themicrophone primarily and directly from the source of the sound andadditionally in the opposite direction therefrom.

It is therefore a general object of this invention to provide a hearingaid to be worn on a persons head as a behind-the-ear type hearing aid orspectacles type hearing aid, having an electro-acoustic transducer withdirectional sound receiving openings arranged in such a manner that thesound appears to come from the direction in which the person wearing thehearing aid is looking.

It is a more specific object of this invention to provide apparatusmaking it possible for the person wearing the hearing aid to locate asource of sound waves by hearing alone in detecting the direction fromwhich the sound is most strongly transmitted.

It is still a further object of this invention to provide a transducerhaving compound diaphragms, one of which is controlled through anaperture and the other of which is controlled through a conduit.

It is still another object of this invention to provide apparatus inwhich the amplitude of sound from opposite 3,458,668 Patented July 29,1969 "ice directions received by the apparatus is controlled by thelength of the sound conduit leading to the apparatus.

These and other objects and advantages of the invention will more fullyappear from the following description, made in connection with theaccompanying drawings, wherein like reference characters refer to thesame or similar parts throughout the several views, and in which:

FIGS. 1 and 2 shown diagrammatic sectional views respectively takenalong the longitudinal center line through a behind-the-ear type hearingaid employing a pair of microphones and a single microphonerespectively;

FIG. 3 shows a sectional view of the mircophone apparatus in accordancewith FIG. 2 taken along the longitudinal center line; and

FIG. 4 is a block diagram of the hearing aid circuit employing thespecial transducer used therein.

The apparatus as shown in FIGS. 1 and 2 shows generally the invention asit is used. A housing 1 which is used to house the hearing aid in abehind-the-ear type hearing aid is curved and adapted to lie behind theauricle of the ear in a manner generally well known. An amplifier 2 iscontained within the hearing aid having a volume control 3 connectedthereto. A battery 4 supplies power to the amplifier and a receiver 5 isdriven by amplifier 2. A hook shaped extension 6 of case or housing 1serves to hold the apparatus over the ear and to pass the sound from thereceiver 5 into the ear of the person Wearing the hearing aid.

As shown in FIG. 1, an opening or aperture 8 is provided in a chamber 7of the hearing aid housing, the opening 8 facing forwardly in the samedirection as the wearers eye detects visible objects. A transducer isformed from a pair of microphones 10 and 11 which may be of the typegenerally known to those skilled in the art which is arranged in a spaceor chamber 7 behind opening 8. Microphone 10 is acoustically secured tothe housing through the use of a seal 9. On the other hand, microphone11 is secured in a back-to-back relationship with a microphone 10 and aconduit or passage 12 is disposed approximately in the longitudinalcenter plane of the housing and is directed rearwardly to an opening 13formed in housing 1. The passage or conduit 12 is formed of a small tubeof elastic material to avoid an acoustic coupling with the housing. Thatis, the feed-back from a mechanical vibration is reduced as much aspossible through the use of the flexible tubing. Thus sound entersopening 8 from the front and is applied directly to microphone 10 Whilesound may enter the rearwardly facing microphone 11 through opening 13and a rather long passage formed by the small tube. The electricaloutputs of both microphones are connected to amplifier 2 in a circuitarrangement to produce a signal which is the combination of the twosounds detected by microphones 10 and 11 respectively. Thus it will beseen that very little sound Will be detected from a transverse directionof the microphone openings while the maximum sound detection will occurat microphone 10 and a secondary sound detection will occur at themicrophone 11. It will be understood that the opening for microphone 11and the passage 12 or flexible tubing are of such size that the soundreceived from the rearward direction is of a smaller amplitude than thatreceived through the front opening 8 and as detected by microphone 10.Using this type of an arrangement, the direction of the sound asdetected by the wearer becomes very perceptible. Using this arrangement,the person Wearing such a hearing aid is afiorded a possibility ofsensing the direction from which the sound emanates so that the personmay turn his head in the direction from Where the sound appears to begenerated and the detection of the sound source may be aided by thevisual sense of the person wearing the hearing aid. The difference inthe amplitude of the signals transmitted from the two microphones may bevaried by changing the relative position of micropone 11 with respect tomicrophone 10 such as shown in the dotted lines Within chamber 7 andcorrespondingly shortening tube 12.

The embodiment shown in FIG. 2 make use of a single microphone ortransducer 14 and is shown in more detail in FIG. 3. Microphone 14 issecured in chamber 7 of the housing 1 directly behind the main opening 8which faces forwardly. Microphone 14 will now be described in moredetail wherein a body 15 has a cover portion 16 secured thereto havingan opening or aperture 17 which lies opposite opening 8 of thehousing 1. A diaphragm 18 is secured to body 15 and will oscillate withthe pressure of the sound waves impinging thereupon. The mechanicaloscillations are transferred to the magnetic system 20 through acoupling pin 19 and the magnetic system is connected with amplifier 2 ina normal manner. A second diaphragm 21 is secured on the opposite sideof magnetic system 20 and diaphragm 21 is coupled with main diaphragm 18by the volume of air trapped in a resonance chamber 22 which is thechamber between the two diaphragms. Sound is directed to diaphragm 21through a rearward opening 23 which is connected with the rearwardhousing opening 13 (FIG. 2) through the use of the flexible tubing 12.By the use of this type of a transducer, the sound waves coming from aposition which is transverse to the direction of orientation of the twomicrophone openings is acoustically reduced or distinguished and thesound waves entering through the front openings 8 and 17 produce asignal of greater magnitude than that received through openings 13 and23, thus providing a device which is sound sensitive and directionoriented.

By the use of the transducers just described, the characteristics of theapparatus is such that the sound pickup has a pattern with lobes such asfound in the figure 8 with the front lobe being considerably larger thanthe lobe to the rear thus providing a maximum degree of sensitivitytowards the front. By selecting the proper length and diameter of thepassage or tube 12, the shape of the lobes and range of frequencieswhich are detectable may be varied. It will also be recognized that bychanging the dimensions of the resonant chamber in the microphonehousing, the characteristics may also be altered.

It should also be recognized that the invention may be used in the samemanner as that just described with a spectacle type hearing aid or anyother hearing air which is worn on the head of a person.

Thus it will be recognized that by the use of the present invention, thesound coming from a predominant source may be readily detected and maybe aided by the visual senses of the wearer in detecting the source ofsound. It will be recognized that by providing a hearing aid in whichthe microphone has both forwardly and rearwardly facing apertures, atruer sound picture is obtained.

It will also be recognized that in the use of the transducer, thatseveral variations may be made such as that shown in FIG. 4 wheremicrophones 10 and 11 are connected to the circuit or where a singlemicrophone such as 14 may be connected to the input of amplifier 2.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the parts withoutdeparting from the scope of my invention which consists of the mattershown and described herein and set forth in the appended claims.

What is claimed is:

1. In a hearing aid housing to be worn on the head of the wearercontaining an amplifier connected to a source of electrical energy and ahearing aid receiver, a transducer comprising:

(a) a microphone mechanism having a pair of apertures disposed in spacedand confronting relationship with a pair of diaphragm members adapted tobe moved by sound waves, said mechanism being secured in the hearing aidhousing;

(b) an acoustic seal disposed around one of said apertures between saidmicrophone mechanism and said hearing aid housing, said housing havingan opening facing forwardly when said hearing aid housing is worn;

(c) and a flexible conduit secured to said microphone mechanism anddisposed in confronting relationship with said other aperture, saidconduit communicating with a rearward facing opening in said hearing aidhousing when worn.

2. The invention as set forth in claim 1 wherein said microphonemechanism includes:

(d) a pair of microphones mounted back-to-back in confrontingrelationship with the apertures of each facing forwardly and rearwardly,and electrically connected to each other in signal aiding relationship.

3. The invention as set forth in claim 2 wherein:

(e) said microphones are disposed in spaced relationship with said rearaperture being further from said rearward facing opening than said frontaperture is from said front opening.

4. The invention as set forth in claim 1 wherein:

(f) said flexible conduit has a greater axial length than said sealbetween said microphone mechanism and said respective openings in saidhearing aid housing.

5. The invention as set forth in claim 1 wherein said flexible conduitincludes:

(g) sound reducting means causing the electrical output signal from saidmicrophone mechanism sensing sound from the rear of said hearing aidhousing to have a smaller magnitude than that sensing around from thefront of said hearing aid.

6. The invention as set forth in claim 1 wherein said microphonemechanism includes:

(h) a single microphone having a pair of diaphragms with a resonantchamber therebetween.

7. The invention as set forth in claim 6 wherein said microphonemechanism includes:

(i) a magnetic system producing output signals representative of soundwaves;

(j) and a coupling device coupling one of said pairs of diaphragms tosaid magnetic system.

References Cited UNITED STATES PATENTS 2,220,208 11/ 1940 Cannon.2,783,312 2/1957 Mouzon. 2,989,597- 6/ 1961 Victoreen.

FOREIGN PATENTS 1,119,918 12/1961 Germany.

KATHLEEN H. CLAFFY, Primary Examiner ARTHUR A. MCGILL, AssistantExaminer US. Cl. X.R. 17912l, 139

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,458,668 July 29, 1969 Otto Hassler It is certified thaterror appears in theabove identified patent and that said Letters Patent are herebycorrected as shown below:

Column 4, line 42, "around" should read sound line 51, "pairs" shouldread pair Signed and sealed this 21st day of April 1970:

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

